Buildings.Experimental.DHC.Networks.Combined.BaseClasses
Package with base classes for Buildings.Experimental.DHC.Networks.Combined
Information
This package contains base classes that are used to construct the models in Buildings.Experimental.DHC.Networks.Combined.
Extends from Modelica.Icons.BasesPackage (Icon for packages containing base classes).
Package Content
| Name | Description |
|---|---|
 ConnectionParallelAutosize
|
Model for connecting an agent to the DHC system |
| ConnectionParallelStandard
|
Model for connecting an agent to the DHC system |
 ConnectionSeriesAutosize
|
Model for connecting an agent to the DHC system |
| ConnectionSeriesStandard
|
Model for connecting an agent to the DHC system |
 PipeAutosize
|
Pipe model parameterized with pressure drop per pipe length |
| PipeStandard
|
Pipe model parameterized with hydraulic diameter |
Buildings.Experimental.DHC.Networks.Combined.BaseClasses.ConnectionParallelAutosize
Model for connecting an agent to the DHC system
Information
This model represents the supply and return lines to connect an agent (e.g., an energy transfer station) to a two-pipe main distribution system. The instances of the pipe model are autosized based on the pressure drop per pipe length at nominal flow rate.
Extends from ConnectionParallelStandard (Model for connecting an agent to the DHC system).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| replaceable package Medium | PartialMedium | Medium model | |
| replaceable model Model_pipDis | PipeAutosize (roughness=7e-6... | ||
| replaceable model Model_pipCon | PipeAutosize (roughness=2.5e... | ||
| Boolean | show_entFlo | false | Set to true to output enthalpy flow rate difference |
| Length | lDis | Length of the distribution pipe before the connection [m] | |
| Length | lCon | Length of the connection pipe (supply only, not counting return line) [m] | |
| Length | dhDis | Hydraulic diameter of the distribution pipe [m] | |
| Length | dhCon | Hydraulic diameter of the connection pipe [m] | |
| Real | dp_length_nominal | 250 | Pressure drop per pipe length at nominal flow rate [Pa/m] |
| Length | dhDisRet | Hydraulic diameter of the return distribution pipe [m] | |
| Nominal condition | |||
| MassFlowRate | mDis_flow_nominal | Nominal mass flow rate in the distribution line [kg/s] | |
| MassFlowRate | mCon_flow_nominal | Nominal mass flow rate in the connection line [kg/s] | |
| Assumptions | |||
| Boolean | allowFlowReversal | false | = true to allow flow reversal, false restricts to design direction (port_a -> port_b) |
| Dynamics | |||
| Conservation equations | |||
| Dynamics | energyDynamics | Modelica.Fluid.Types.Dynamic... | Type of energy balance: dynamic (3 initialization options) or steady state |
| Nominal condition | |||
| Time | tau | 5*60 | Time constant at nominal flow for dynamic energy and momentum balance [s] |
Connectors
| Type | Name | Description |
|---|---|---|
| replaceable model Model_pipDis | ||
| replaceable model Model_pipCon | ||
| FluidPort_a | port_aDisSup | Distribution supply inlet port |
| FluidPort_b | port_bDisSup | Distribution supply outlet port |
| FluidPort_a | port_aDisRet | Distribution return inlet port |
| FluidPort_b | port_bDisRet | Distribution return outlet port |
| FluidPort_b | port_bCon | Connection supply port |
| FluidPort_a | port_aCon | Connection return port |
| output RealOutput | mCon_flow | Connection supply mass flow rate [kg/s] |
| output RealOutput | dp | Pressure drop accross the connection (measured) [Pa] |
| output RealOutput | dH_flow | Difference in enthalpy flow rate between connection supply and return [W] |
Modelica definition
model ConnectionParallelAutosize
"Model for connecting an agent to the DHC system"
extends ConnectionParallelStandard(
tau=5*60,
redeclare replaceable model Model_pipDis = PipeAutosize (
roughness=7e-6,
fac=1.5,
dh(fixed=true)=dhDis,
final length=lDis,
final dp_length_nominal=dp_length_nominal),
pipDisRet(dh=dhDisRet),
redeclare replaceable model Model_pipCon = PipeAutosize (
roughness=2.5e-5,
fac=2,
final length=2*lCon,
final dh(fixed=true)=dhCon,
final dp_length_nominal=dp_length_nominal));
parameter Real dp_length_nominal(final unit="Pa/m") = 250
"Pressure drop per pipe length at nominal flow rate";
parameter Modelica.Units.SI.Length dhDisRet
"Hydraulic diameter of the return distribution pipe";
end ConnectionParallelAutosize;
Buildings.Experimental.DHC.Networks.Combined.BaseClasses.ConnectionParallelStandard
Model for connecting an agent to the DHC system
Information
This model represents the supply and return lines to connect an agent (e.g., an energy transfer station) to a two-pipe main distribution system. The instances of the pipe model are parameterized with the hydraulic diameter.
Extends from Buildings.Experimental.DHC.Networks.BaseClasses.PartialConnection2Pipe (Partial model for connecting an agent to a two-pipe distribution network).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| replaceable package Medium | PartialMedium | Medium model | |
| replaceable model Model_pipDis | PipeStandard (roughness=7e-6... | ||
| replaceable model Model_pipCon | PipeStandard (roughness=2.5e... | ||
| Boolean | show_entFlo | false | Set to true to output enthalpy flow rate difference |
| Length | lDis | Length of the distribution pipe before the connection [m] | |
| Length | lCon | Length of the connection pipe (supply only, not counting return line) [m] | |
| Length | dhDis | Hydraulic diameter of the distribution pipe [m] | |
| Length | dhCon | Hydraulic diameter of the connection pipe [m] | |
| Nominal condition | |||
| MassFlowRate | mDis_flow_nominal | Nominal mass flow rate in the distribution line [kg/s] | |
| MassFlowRate | mCon_flow_nominal | Nominal mass flow rate in the connection line [kg/s] | |
| Assumptions | |||
| Boolean | allowFlowReversal | false | = true to allow flow reversal, false restricts to design direction (port_a -> port_b) |
| Dynamics | |||
| Conservation equations | |||
| Dynamics | energyDynamics | Modelica.Fluid.Types.Dynamic... | Type of energy balance: dynamic (3 initialization options) or steady state |
| Nominal condition | |||
| Time | tau | 5*60 | Time constant at nominal flow for dynamic energy and momentum balance [s] |
Connectors
| Type | Name | Description |
|---|---|---|
| replaceable model Model_pipDis | ||
| replaceable model Model_pipCon | ||
| FluidPort_a | port_aDisSup | Distribution supply inlet port |
| FluidPort_b | port_bDisSup | Distribution supply outlet port |
| FluidPort_a | port_aDisRet | Distribution return inlet port |
| FluidPort_b | port_bDisRet | Distribution return outlet port |
| FluidPort_b | port_bCon | Connection supply port |
| FluidPort_a | port_aCon | Connection return port |
| output RealOutput | mCon_flow | Connection supply mass flow rate [kg/s] |
| output RealOutput | dp | Pressure drop accross the connection (measured) [Pa] |
| output RealOutput | dH_flow | Difference in enthalpy flow rate between connection supply and return [W] |
Modelica definition
model ConnectionParallelStandard
"Model for connecting an agent to the DHC system"
extends Buildings.Experimental.DHC.Networks.BaseClasses.PartialConnection2Pipe
(
tau=5*60,
redeclare replaceable model Model_pipDis = PipeStandard (
roughness=7e-6,
fac=1.5,
final length=lDis,
final dh=dhDis),
redeclare replaceable model Model_pipCon = PipeStandard (
roughness=2.5e-5,
fac=2,
final length=2*lCon,
final dh=dhCon));
parameter Modelica.Units.SI.Length lDis
"Length of the distribution pipe before the connection";
parameter Modelica.Units.SI.Length lCon
"Length of the connection pipe (supply only, not counting return line)";
parameter Modelica.Units.SI.Length dhDis
"Hydraulic diameter of the distribution pipe";
parameter Modelica.Units.SI.Length dhCon
"Hydraulic diameter of the connection pipe";
end ConnectionParallelStandard;
Buildings.Experimental.DHC.Networks.Combined.BaseClasses.ConnectionSeriesAutosize
Model for connecting an agent to the DHC system
Information
This model represents the supply and return lines to connect an agent (e.g., an energy transfer station) to a one-pipe main distribution system. The instances of the pipe model are autosized based on the pressure drop per pipe length at nominal flow rate.
Extends from ConnectionSeriesStandard (Model for connecting an agent to the DHC system).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| replaceable package Medium | PartialMedium | Medium model | |
| replaceable model Model_pipDis | PipeAutosize (roughness=7e-6... | ||
| replaceable model Model_pipCon | PipeAutosize (roughness=2.5e... | ||
| Boolean | show_entFlo | false | Set to true to output enthalpy flow rate difference |
| Boolean | show_TOut | false | Set to true to output temperature at connection outlet |
| MassFlowRate | mDis_flow_nominal | Nominal mass flow rate in the distribution line [kg/s] | |
| MassFlowRate | mCon_flow_nominal | Nominal mass flow rate in the connection line [kg/s] | |
| Length | lDis | Length of the distribution pipe before the connection [m] | |
| Length | lCon | Length of the connection pipe (supply only, not counting return line) [m] | |
| Length | dhDis | Hydraulic diameter of the distribution pipe [m] | |
| Length | dhCon | Hydraulic diameter of the connection pipe [m] | |
| Real | dp_length_nominal | 250 | Pressure drop per pipe length at nominal flow rate [Pa/m] |
| Assumptions | |||
| Boolean | allowFlowReversal | false | = true to allow flow reversal, false restricts to design direction (port_a -> port_b) |
| Dynamics | |||
| Conservation equations | |||
| Dynamics | energyDynamics | Modelica.Fluid.Types.Dynamic... | Type of energy balance: dynamic (3 initialization options) or steady state |
| Nominal condition | |||
| Time | tau | 5*60 | Time constant at nominal flow for dynamic energy and momentum balance [s] |
Connectors
| Type | Name | Description |
|---|---|---|
| replaceable model Model_pipDis | ||
| replaceable model Model_pipCon | ||
| FluidPort_a | port_aDis | Distribution inlet port |
| FluidPort_b | port_bDis | Distribution outlet port |
| FluidPort_a | port_aCon | Connection return port |
| FluidPort_b | port_bCon | Connection supply port |
| output RealOutput | mCon_flow | Connection supply mass flow rate (measured) [kg/s] |
| output RealOutput | dH_flow | Difference in enthalpy flow rate between connection supply and return [W] |
| output RealOutput | mByp_flow | Bypass mass flow rate [kg/s] |
| output RealOutput | TOut | Temperature in distribution line at connection outlet [K] |
Modelica definition
model ConnectionSeriesAutosize
"Model for connecting an agent to the DHC system"
extends ConnectionSeriesStandard(
tau=5*60,
redeclare replaceable model Model_pipDis = PipeAutosize (
roughness=7e-6,
fac=1.5,
final length=lDis,
final dh(fixed=true)=dhDis,
final dp_length_nominal=dp_length_nominal),
redeclare replaceable model Model_pipCon = PipeAutosize (
roughness=2.5e-5,
fac=2,
final length=2*lCon,
final dh(fixed=true)=dhCon,
final dp_length_nominal=dp_length_nominal));
parameter Real dp_length_nominal(final unit="Pa/m") = 250
"Pressure drop per pipe length at nominal flow rate";
end ConnectionSeriesAutosize;
Buildings.Experimental.DHC.Networks.Combined.BaseClasses.ConnectionSeriesStandard
Model for connecting an agent to the DHC system
Information
This model represents the supply and return lines to connect an agent (e.g., an energy transfer station) to a one-pipe main distribution system. The instances of the pipe model are parameterized with the hydraulic diameter.
Extends from Buildings.Experimental.DHC.Networks.BaseClasses.PartialConnection1Pipe (Partial model for connecting an agent to a one-pipe distribution network).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| replaceable package Medium | PartialMedium | Medium model | |
| replaceable model Model_pipDis | PipeStandard (roughness=7e-6... | ||
| replaceable model Model_pipCon | PipeStandard (roughness=2.5e... | ||
| Boolean | show_entFlo | false | Set to true to output enthalpy flow rate difference |
| Boolean | show_TOut | false | Set to true to output temperature at connection outlet |
| MassFlowRate | mDis_flow_nominal | Nominal mass flow rate in the distribution line [kg/s] | |
| MassFlowRate | mCon_flow_nominal | Nominal mass flow rate in the connection line [kg/s] | |
| Length | lDis | Length of the distribution pipe before the connection [m] | |
| Length | lCon | Length of the connection pipe (supply only, not counting return line) [m] | |
| Length | dhDis | Hydraulic diameter of the distribution pipe [m] | |
| Length | dhCon | Hydraulic diameter of the connection pipe [m] | |
| Assumptions | |||
| Boolean | allowFlowReversal | false | = true to allow flow reversal, false restricts to design direction (port_a -> port_b) |
| Dynamics | |||
| Conservation equations | |||
| Dynamics | energyDynamics | Modelica.Fluid.Types.Dynamic... | Type of energy balance: dynamic (3 initialization options) or steady state |
| Nominal condition | |||
| Time | tau | 5*60 | Time constant at nominal flow for dynamic energy and momentum balance [s] |
Connectors
| Type | Name | Description |
|---|---|---|
| replaceable model Model_pipDis | ||
| replaceable model Model_pipCon | ||
| FluidPort_a | port_aDis | Distribution inlet port |
| FluidPort_b | port_bDis | Distribution outlet port |
| FluidPort_a | port_aCon | Connection return port |
| FluidPort_b | port_bCon | Connection supply port |
| output RealOutput | mCon_flow | Connection supply mass flow rate (measured) [kg/s] |
| output RealOutput | dH_flow | Difference in enthalpy flow rate between connection supply and return [W] |
| output RealOutput | mByp_flow | Bypass mass flow rate [kg/s] |
| output RealOutput | TOut | Temperature in distribution line at connection outlet [K] |
Modelica definition
model ConnectionSeriesStandard
"Model for connecting an agent to the DHC system"
extends Buildings.Experimental.DHC.Networks.BaseClasses.PartialConnection1Pipe
(
tau=5*60,
redeclare replaceable model Model_pipDis = PipeStandard (
roughness=7e-6,
fac=1.5,
final length=lDis,
final dh=dhDis),
redeclare replaceable model Model_pipCon = PipeStandard (
roughness=2.5e-5,
fac=2,
final length=2*lCon,
final dh=dhCon));
parameter Modelica.Units.SI.Length lDis
"Length of the distribution pipe before the connection";
parameter Modelica.Units.SI.Length lCon
"Length of the connection pipe (supply only, not counting return line)";
parameter Modelica.Units.SI.Length dhDis
"Hydraulic diameter of the distribution pipe";
parameter Modelica.Units.SI.Length dhCon
"Hydraulic diameter of the connection pipe";
end ConnectionSeriesStandard;
Buildings.Experimental.DHC.Networks.Combined.BaseClasses.PipeAutosize
Pipe model parameterized with pressure drop per pipe length
Information
This model is similar to Buildings.Fluid.FixedResistances.HydraulicDiameter except for the modifications below which allow to use this model for computing the hydraulic diameter at initialization, based on the pressure drop per pipe length at nominal flow rate.
-
The parameter
v_nominalis computed based on the nominal flow rate. -
The equation
dp_nominal = fac*dpStraightPipe_nominalis solved at initialization for the hydraulic diameterdh. -
The parameter
dp_nominalis assigned a value that does not need to be computed at initialization. This is required per Modelica specification because the structural parametercomputeFlowResistancedepends ondp_nominaland must be evaluated at compile time.
Extends from Buildings.Fluid.FixedResistances.PressureDrop (Fixed flow resistance with dp and m_flow as parameter).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| replaceable package Medium | PartialMedium | Medium in the component | |
| Length | dh | Hydraulic diameter (assuming a round cross section area) [m] | |
| Real | dp_length_nominal | 250 | Pressure drop per pipe length at nominal flow rate [Pa/m] |
| Length | length | Length of the pipe [m] | |
| Real | ReC | 4000 | Reynolds number where transition to turbulence starts |
| Length | roughness | 2.5e-5 | Absolute roughness of pipe, with a default for a smooth steel pipe (PE100: 7E-6) [m] |
| Real | fac | 2 | Factor to take into account resistance of bends etc., fac=dp_nominal/dpStraightPipe_nominal |
| Nominal condition | |||
| MassFlowRate | m_flow_nominal | Nominal mass flow rate [kg/s] | |
| PressureDifference | dp_nominal | dp_length_nominal*length | Pressure drop at nominal mass flow rate [Pa] |
| Velocity | v_nominal | m_flow_nominal/(rho_default*... | Velocity at m_flow_nominal (used to compute default value for hydraulic diameter dh) [m/s] |
| Transition to laminar | |||
| Real | deltaM | eta_default*dh/4*Modelica.Co... | Fraction of nominal mass flow rate where transition to turbulent occurs |
| Assumptions | |||
| Boolean | allowFlowReversal | true | = false to simplify equations, assuming, but not enforcing, no flow reversal |
| Advanced | |||
| Diagnostics | |||
| Boolean | show_T | false | = true, if actual temperature at port is computed |
| Boolean | from_dp | false | = true, use m_flow = f(dp) else dp = f(m_flow) |
| Boolean | linearized | false | = true, use linear relation between m_flow and dp for any flow rate |
Connectors
| Type | Name | Description |
|---|---|---|
| FluidPort_a | port_a | Fluid connector a (positive design flow direction is from port_a to port_b) |
| FluidPort_b | port_b | Fluid connector b (positive design flow direction is from port_a to port_b) |
Modelica definition
model PipeAutosize "Pipe model parameterized with pressure drop per pipe length"
extends Buildings.Fluid.FixedResistances.PressureDrop(
final deltaM = eta_default*dh/4*Modelica.Constants.pi*ReC/m_flow_nominal_pos,
final dp_nominal=dp_length_nominal*length);
parameter Modelica.Units.SI.Length dh(
fixed=false,
start=0.05,
min=0.01) "Hydraulic diameter (assuming a round cross section area)";
parameter Real dp_length_nominal(final unit="Pa/m") = 250
"Pressure drop per pipe length at nominal flow rate";
parameter Modelica.Units.SI.Length length "Length of the pipe";
parameter Real ReC(min=0)=4000
"Reynolds number where transition to turbulence starts";
parameter Modelica.Units.SI.Velocity v_nominal=m_flow_nominal/(rho_default*
ARound)
"Velocity at m_flow_nominal (used to compute default value for hydraulic diameter dh)";
parameter Modelica.Units.SI.Length roughness(min=0) = 2.5e-5
"Absolute roughness of pipe, with a default for a smooth steel pipe (PE100: 7E-6)";
parameter Real fac(min=1) = 2
"Factor to take into account resistance of bends etc., fac=dp_nominal/dpStraightPipe_nominal";
final parameter Modelica.Units.SI.PressureDifference dpStraightPipe_nominal(
displayUnit="Pa")=
Modelica.Fluid.Pipes.BaseClasses.WallFriction.Detailed.pressureLoss_m_flow(
m_flow=m_flow_nominal,
rho_a=rho_default,
rho_b=rho_default,
mu_a=mu_default,
mu_b=mu_default,
length=length,
diameter=dh,
roughness=roughness,
m_flow_small=m_flow_small)
"Pressure loss of a straight pipe at m_flow_nominal";
Modelica.Units.SI.Velocity v=m_flow/(rho_default*ARound)
"Flow velocity (assuming a round cross section area)";
protected
parameter Modelica.Units.SI.Area ARound=dh^2*Modelica.Constants.pi/4
"Cross sectional area (assuming a round cross section area)";
parameter Medium.ThermodynamicState state_default=
Medium.setState_pTX(
T=Medium.T_default,
p=Medium.p_default,
X=Medium.X_default[1:Medium.nXi]) "Default state";
parameter Modelica.Units.SI.Density rho_default=Medium.density(state_default)
"Density at nominal condition";
parameter Modelica.Units.SI.DynamicViscosity mu_default=
Medium.dynamicViscosity(state_default)
"Dynamic viscosity at nominal condition";
initial equation
dp_nominal = fac*dpStraightPipe_nominal;
end PipeAutosize;
Buildings.Experimental.DHC.Networks.Combined.BaseClasses.PipeStandard
Pipe model parameterized with hydraulic diameter
Information
This model is similar to Buildings.Fluid.FixedResistances.HydraulicDiameter except that a binding equation is provided to compute the nominal fluid velocity from the hydraulic diameter (as opposed to the hydraulic diameter being computed from the nominal fluid velocity in the original model).
Extends from Buildings.Fluid.FixedResistances.HydraulicDiameter (Fixed flow resistance with hydraulic diameter and m_flow as parameter).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| replaceable package Medium | PartialMedium | Medium in the component | |
| Length | dh | sqrt(4*m_flow_nominal/rho_de... | Hydraulic diameter (assuming a round cross section area) [m] |
| Length | length | Length of the pipe [m] | |
| Real | ReC | 4000 | Reynolds number where transition to turbulence starts |
| Length | roughness | 2.5e-5 | Absolute roughness of pipe, with a default for a smooth steel pipe (dummy if use_roughness = false) [m] |
| Real | fac | 2 | Factor to take into account resistance of bends etc., fac=dp_nominal/dpStraightPipe_nominal |
| Nominal condition | |||
| MassFlowRate | m_flow_nominal | Nominal mass flow rate [kg/s] | |
| Velocity | v_nominal | m_flow_nominal*4/(rho_defaul... | Velocity at m_flow_nominal (used to compute default value for hydraulic diameter dh) [m/s] |
| Assumptions | |||
| Boolean | allowFlowReversal | true | = false to simplify equations, assuming, but not enforcing, no flow reversal |
| Advanced | |||
| Diagnostics | |||
| Boolean | show_T | false | = true, if actual temperature at port is computed |
| Boolean | from_dp | false | = true, use m_flow = f(dp) else dp = f(m_flow) |
| Boolean | linearized | false | = true, use linear relation between m_flow and dp for any flow rate |
Connectors
| Type | Name | Description |
|---|---|---|
| FluidPort_a | port_a | Fluid connector a (positive design flow direction is from port_a to port_b) |
| FluidPort_b | port_b | Fluid connector b (positive design flow direction is from port_a to port_b) |
Modelica definition
model PipeStandard "Pipe model parameterized with hydraulic diameter"
extends Buildings.Fluid.FixedResistances.HydraulicDiameter(
dp(nominal=1E5),
final linearized=false,
final v_nominal=m_flow_nominal * 4 / (rho_default * dh^2 * Modelica.Constants.pi));
end PipeStandard;